1. Field of the Invention
The present invention relates generally to hosiery, and more particularly, to a knitted compression article for improved vascular health.
2. Description of the Prior Art
Prior art compression hose are designed as support devices worn on the legs, and used to compensate for the widely-incurred and age-related biologic deterioration of blood return from the legs. Consistent with physiologic patterns throughout the human body, the legs receive blood via the arterial system, and return it through the venous channels back to the heart. The ubiquitous exit vessels (veins) are comprised in a coupled parallel arrangement, termed the superficial and deep systems. The two systems communicate via venous perforators, which arrange themselves similar to a scaffold. Within the lumen of the superficial system (called the greater and lesser saphenous veins, residing in front and behind the leg respectively) there exists a tiny assemblage of one-way valves. These function to orchestrate a through passage of blood such that after flowing arterially to the soft tissues of the leg and distally to the feet, effluent venous drainage is continuously collected in the superficial venous system(s), routed via perforators to the central deep system (not visible externally and residing nearer the central core of the leg) and directed back to the heart. There are also valves within the deep system. Working responsively with the squeezing and relaxing leg muscles which compress the intervalvular venous segments, the valves maintain return as a one-way process with the majority of the venous blood flowing in response to this muscular contraction. When the legs are at rest, normal (competent) valves close and forward motion ebbs, but backflow is prevented. With leg activity and muscular contraction, the veins are squeezed by the leg muscles causing the valves to open and facilitate forward blood return through communicating branches to the parallel deep system, and thence to the heart.
Unfortunately, with the development of the common pathologic condition addressed herein and termed “valvular incompetence,” this physiologic one-way functionality degenerates. When the valves lose competence, they are unable to prevent blood flow back toward the feet. This problem is exacerbated by prolonged sitting or standing situations where gravity also encourages backflow. Progressively, the superficial system (visible externally) sustains debilitative venous hypertension and stasis, leading to tissue edema, varicosity formation and other damaging sequellae. Compression hosiery garments are designed to substitute for the incompetent superficial venous valve function, and rectify the resultant pooling tendencies by coercing the transference of venous blood from this impaired superficial system into the deep system. This is achieved through the external application of a longitudinally graduated and centrally-directed radial force. The superficial venous distension is thereby retarded, blood pooling minimized and venous stasis consequences subdued.
While compression stockings as in the prior art are widely used and do reliably mitigate this superficial venous hypertension, a regimen of multi-hour or all-day wear is typically required. Most users resist wearing prior art compression stockings for extended and possibly chronic periods, largely because of an attendant discomfort. In the prior art, a cephalad blood flow trajectory is reinstated with a crude compression gradient which decreases linearly from ankle to groin. The garments are usually marketed in either knee-high or thigh-high options, the latter generally recommended for the more severe cases of venous stasis. As such, this prior art compression hosiery is imperfectly designed with respect to certain important anatomic features, and these design elements likely contribute to the attendant discomfort. An average set of compression hosiery consists of a 40 mmHg radial force applied at the ankle, with a linear 70% reduction to the top of the garment that may extend either to the knee or to the thigh. The uniform gradient slope of the prior art compression, is conceptually inconsistent with the normal anatomic pattern of the venous valves intended to be compensated for. While studies are few, it has been shown that the numeric density of the valve system below the knee (5-7 valves) is very different from that above the knee (approx. 3 valves). Because the superficial venous valves are numerically more populous below the knee than above, the force vector imparted is more vigorously structured between ankle and knee (calf) than between knee and groin (thigh). Additionally, the lower leg musculofascial architecture is denser than that of the thigh, bringing about an augmented relationship of the veins with the propulsive muscles. More importantly, current knee-high design sharply ends compression just below the tibial plateau, where the superficial system insinuates deeply and among the ligaments and bony prominences of the knee joint complex. Wearers of knee-high compression hosiery almost universally note a very uncomfortable constrictive effect at that point.
Both the failure of compression hosiery design to recapitulate the inherent differences between the below knee and above knee anatomy, and the common knee high design pattern of ending at the tibial plateau, likely reduce garment efficacy and wearer comfort. Inappropriately high thigh compression is unpleasant and may actually retard venous return; inadequate calf gradients are likely ineffective, and straight-line compression declination mandates one or both of these conditions. There remains, therefore, a need for attractively-patterned, medically functional compression hosiery that restores the one-way valvular effects through appropriate compression gradient slopes which respect the nonlinear valvular cadence throughout the human leg. In addition, structural avoidance of the constrictive effect at the tibial plateau will lend itself to increased patient compliance.
Examples of relevant documents from the prior art include: U.S. Pat. No. 5,989,948 describes a support sock made of elastomeric material and designed to enhance athletic performance, including a sock with a pressure gradient with the maximum pressure exhibited at the foot portion and a minimum pressure at the proximal end, as well as a distinct foot portion of the sock and biomechanical supports to stabilize muscle and tendon groups during activity; U.S. Pat. Nos. 6,572,574 and 6,371,933, and US Patent Application Publication No. 20020029012 for a compressive orthosis of the sock type for treating circulatory disease of the lower limbs, in particular for applying compressive support to the leg after venous ulcer, which teaches an orthosis designed to apply graduated compression beginning with the greatest pressure at the foot or ankle, including a sock with a leg portion made of knitted compression material; US Patent Application Publication No. 20080171959 for a compression article, particularly a compression stocking with a surface pattern, describes a compression stocking or tights made of elastic knitted fabric, wherein additional knitting is done to obtain a surface pattern including chessboards, stripes, argyle, bubble or circles.
Other references exemplary of prior art compression stockings include: U.S. Pat. Nos. 7,441,419, 7,117,695, 6,725,691, 6,613,007, 6,572,437, and 6,216,495.
While compression articles like these are known in the art, and surface patterned knitting is known, the combination fails to deliver compression gradients that simulate the body's valve-based system from foot toward the knee area, and from thence to the thigh, and therefore fail to perform or function in a manner that replicates it. In addition, there are few commercially available knee-high style garments that continue their compression to some level above the knee, thereby avoiding the constrictive effect at the tibial plateau. Thus, there remains a need in the art for compression knitted articles for application in lower leg (knee high) to total leg (thigh high) coverage, which simulate the inhomogeneous venous valve distribution through a nonlinearly sloped pressure gradient, maintains compression cephalad to the knee joint at a physiologic gradient slope in both the knee high and thigh high versions.